split_link tool, config, and scripts for windows build

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 91bb896a63daf18284de29090294cdbedcca53ca..0e3ee43c3bccfcf0c3f13cbcc5fdef089f6d7043 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -910,8 +910,8 @@
     # to get incremental linking to be faster in debug builds.
     'incremental_chrome_dll%': '0',
 
-    # Experimental setting to break chrome.dll in to chrome_browser.dll and
-    # chrome_child.dll.
+    # Experimental setting to break chrome.dll in to multiple parts (currently
+    # two, split primarily along browser/render lines).
     'chrome_split_dll%': '0',
 
     # The default settings for third party code for treating
@@ -1836,7 +1836,9 @@
         ],
       }],
       ['chrome_split_dll', {
-        'defines': ['CHROME_SPLIT_DLL'],
+        'variables': {
+          'chrome_split_dll': '<!(python <(DEPTH)/tools/win/split_link/check_installed.py)',
+        }
       }],
       ['OS=="linux" and clang==1 and host_arch=="ia32"', {
         # TODO(dmikurube): Remove -Wno-sentinel when Clang/LLVM is fixed.